The present invention relates to a heat exchanger and to a method of manufacturing the same. More particularly, the present invention relates to a heat exchanger which is used as a condenser for a car air conditioner mounted on a vehicle such as an automobile, and to a method of manufacturing the heat exchanger.
In this specification and claims, the term “aluminum” encompasses aluminum alloys in addition to pure aluminum. Also, materials represented by chemical symbols represent pure materials, and the term “Al alloy” means an aluminum alloy.
There has been known a heat exchanger which has the following structure and is used as a condenser for a car air conditioner (see Japanese Patent Application Laid-Open (kokai) No. H09-113177). The heat exchanger has a plurality of flat heat exchange tubes formed of an aluminum extrudate, header tanks, corrugated aluminum fins, and aluminum side plates. The flat heat exchange tubes are disposed at predetermined intervals in the thickness direction such that their longitudinal directions coincide with one another and their width directions coincide with an air-flow direction. The header tanks are disposed at opposite longitudinal ends of the heat exchange tubes such that their longitudinal directions coincide with the direction in which the heat exchange tubes are juxtaposed. Opposite ends of the heat exchange tubes are connected to the corresponding header tanks. Each of the fins is disposed between adjacent heat exchange tubes or on the outer side of the heat exchange tube at each of opposite ends, and is brazed to the corresponding heat exchange tube(s). The side plates are disposed outward of the fins at opposite ends and are brazed to the corresponding fins. Each of the header tanks is composed of a tubular tank body formed of aluminum and closing members formed of aluminum. The tank body is formed by bending, into a tubular shape, an aluminum brazing sheet having a brazing material layer on each of opposite sides thereof and brazing opposite side edges of the sheet which are butted against each other. The tank body has openings at opposite ends thereof. The closing members are brazed to the opposite ends of the tank body so as to close the openings at the opposite ends. The tank body has a plurality of tube insertion holes (through holes) elongated in the air-flow direction and spaced from one another in the longitudinal direction of the tank body. Protrusion portions protruding toward the inner space of the tank body are integrally formed along edges of each tube insertion hole which are located on opposite sides in the width direction and which face each other. An end portion of each heat exchange tube is inserted into the corresponding tube insertion hole and is brazed to a portion of the tank body around the tube insertion hole and to the corresponding protrusion portions.
The heat exchanger disclosed in the publication is manufactured by a method which includes simultaneous brazing of heat exchange tubes, tank body members, closing members, fines, and side plates. Each tank body member is formed by bending, into a tubular shape, an aluminum brazing sheet having a brazing material layer on each of opposite sides thereof, and opposite side edges of the member butted against each other are not brazed together.
In recent years, heat exchangers have been demanded to have an enhanced performance, a reduced weight, and a reduced size. A conceivable way to satisfy such demand is decreasing the thickness of the wall of each heat exchange tube and decreasing the tube height which is the dimension of each heat exchange tube in the thickness direction. However, in the case of heat exchange tubes formed of aluminum extrudate, there arises a problem in that when a decreased wall thickness of each heat exchange tube and a decreased tube height which is the dimension of each heat exchange tube in the thickness direction are realized, production cost increases.
In view of this, there has been proposed a flat heat exchange tube which can decrease the tube wall thickness and the tube height while suppressing an increase in production cost (see Japanese Patent Application Laid-Open (kokai) No. 2009-168360).
The flat heat exchange tube disclosed in the publication is formed by bending an aluminum brazing sheet having a brazing material layer on each of opposite sides thereof and brazing portions of the sheet which are to be joined. The heat exchange tube has a pair of flat walls facing each other, two side walls provided between opposite side edges of the two flat walls, and a wavy partition member which divides the internal space into a plurality of refrigerant passages extending in the length direction of the tube. Each of the flat walls is formed as a single member as a whole. The two side walls are flat and extend in the height direction of the tube. One side wall is integrally provided between one side edge of one flat wall and one side edge of the other flat wall, and the other side wall is integrally provided at the other side edge of the one flat wall. A flat reinforcing member extending in the tube height direction is integrally provided at the side edge of the other flat wall on the side where the other side wall is present. The partition member is integrally formed such that the partition member extends from the distal end of the reinforcing member toward the one side wall. Another flat reinforcing member extending in the tube height direction is integrally provided at the side edge of the partition member on the side where the one side wall is present. The two side walls and the two reinforcing members are overlaid and brazed together in such a manner that one side wall and the corresponding reinforcing member come into contact with each other and form a layered structure. The partition member has a wavy shape and has a plurality of partition walls and connection portions. The partition walls extend in the tube length direction, are juxtaposed in the width direction of the tube, and each separates adjacent refrigerant passages from each other. The connection portions of the partition member connect adjacent partition walls together and are joined to the inner surfaces of the two flat walls. The connection portions of the partition member located on one side in the tube height direction are brazed to the one flat wall, and the connection portions of the partition member located on the other side in the tube height direction are brazed to the other flat wall.
In the case where the heat exchange tube disclosed in Japanese Patent Application Laid-Open No. 2009-168360 is applied to the heat exchange tube disclosed in Japanese Patent Application Laid-Open No. H09-113177, the heat exchanger is manufactured by the following method. Specifically, through use of an aluminum brazing sheet having a brazing material layer on each of opposite sides thereof, heat exchange tube members and tank body members are manufactured. Each of the heat exchange tube members is a bent member which is to become a flat heat exchange tube and in which the two side walls and the two reinforcing members are not brazed and the two flat walls and the connection portions of the partition member are not brazed. Each of the tank body members has opposite side edges which are butted against each other but are not brazed together, and has tube insertion holes and protrusion portions. The heat exchange tube members, the fins, and the side plates are combined together, and the tank body members and the closing members are combined together. Subsequently, after opposite end portions of the heat exchange tube members are inserted into the tube insertion holes of the tank body members, the two side walls and the two reinforcing members of each heat exchange tube member are brazed together and the two flat walls and the connection portions of the partition member are brazed together, whereby the heat exchange tubes are made. Further, the butted portions of each tank body member are brazed together to form a tank body. Also, the tank body and the closing members are brazed together so as to produce each of the header tanks. Simultaneously, the heat exchange tubes and the fins are brazed together, the fins and the side plates are brazed together, and the heat exchange tubes are brazed to portions of the tank bodies around the tube insertion holes and to the protrusion portions whereby the heat exchanger is manufactured.
Although not clearly shown in the above-mentioned two publications, the brazing material covering the outer surface of the tank body member of each header tank and the brazing material covering the outer surface of each heat exchange tube member have similar degrees of flowability when melted.
However, in this case, when brazing is performed, the brazing material covering the outer surface of the tank body member of each header tank melts, and the molten brazing material flows toward the heat exchange tube members which form the heat exchange tubes, whereby the amount of the brazing material becomes excessive, which causes a problem in that erosion becomes more likely to occur in a region of the outer circumferential surface of each heat exchange tube formed from the heat exchange tube member, the region being located near the corresponding header tank.